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 A068997 Numbers n such that Sum_{d|n} d*mu(d) divides n. 5
 1, 2, 4, 6, 8, 12, 16, 18, 20, 24, 32, 36, 40, 48, 54, 64, 72, 80, 84, 96, 100, 108, 120, 128, 144, 160, 162, 168, 192, 200, 216, 240, 252, 256, 272, 288, 312, 320, 324, 336, 360, 384, 400, 432, 440, 480, 486, 500, 504, 512, 544, 576, 588, 600, 624, 640, 648 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The only squarefree terms so far are a(1), a(2), and a(4). - Torlach Rush, Dec 04 2017 There is a surjective mapping from all even numbers not in this sequence to terms of the sequence. The first such is 10 to a(9). The next is 14,28,42 to a(19). All even numbers not in the sequence are divisors of some term in the sequence. - Torlach Rush, Dec 08 2017 LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 FORMULA n such that A023900(n) divides n. MAPLE with(numtheory): A068997 := i->`if`(i mod phi(mul(j, j=factorset(i)))=0, i, NULL): seq(A068997(i), i=1..650); # Peter Luschny, Nov 02 2010 MATHEMATICA Select[Range[650], Divisible[#, DivisorSum[#, # MoebiusMu[#] &]] &] (* Michael De Vlieger, Nov 20 2017 *) PROG (PARI) for(n=1, 1000, if(n%sumdiv(n, d, moebius(d)*d)==0, print1(n, ", "))) (Haskell) a068997 n = a068997_list !! (n - 1) a068997_list = filter (\x -> mod x (a173557 x) == 0) [1..] -- Reinhard Zumkeller, Jun 01 2015 CROSSREFS Cf. A173557. Sequence in context: A124240 A320580 A325763 * A293928 A067712 A060765 Adjacent sequences: A068994 A068995 A068996 * A068998 A068999 A069000 KEYWORD easy,nonn AUTHOR Benoit Cloitre, Apr 07 2002 STATUS approved

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Last modified March 21 18:35 EDT 2023. Contains 361410 sequences. (Running on oeis4.)